This invention relates to a printer, and more particularly to a printer which can print in two colors using alternatively usable ink rolls having different color inks thereon.
Where record paper is printed alternatively with, for example, black ink and red ink, printers of the ink ribbon type are used commonly. A two color printer of the ink ribbon type normally includes a fabric ribbon having two upper and lower ink zones of black ink and red ink impregnated in a fabric ribbon in the form of a roll, a ribbon feed mechanism for feeding the fabric ribbon in a predetermined direction, and an ink changeover mechanism for shifting the fabric ribbon in a direction corresponding to the paper feeding direction to change over the ink zone relative to a type wheel, whereby an impact force of a hammer acts upon the type wheel via the record paper and the fabric ribbon to transfer the ink of a desired color on the fabric ribbon to the record paper.
However, in such a two color printer of the ink ribbon type wherein a fabric ribbon is used, ink impregnated in a fabric is squeezed out therefrom by a pressing force between a hammer and a type wheel to transfer the ink to record paper. Accordingly, the printer has drawbacks that clear results of printing can be seldom attained and that a strong force is required for printing.
Thus, a two color printer of the ink roll type has been proposed which uses two ink rolls in which inks of desired colors are impregnated and wherein ink of a desired one of the colors is applied to character type elements of a type wheel and then record paper is pressure contacted with one of the character type elements by a hammer to print a character on the record paper. According to the two color printer of the ink roll type, ink applied to the character type elements of the type wheel is transferred to record paper, and hence, clearer results of printing can be attained comparing with a two color printer of the ink ribbon type. Besides, while the cost of an ink roll itself is high compared with a fabric ribbon, the running cost of using an ink roll is reduced because the maximum printable characters is greater than for a ribbon cassette. In addition, a ribbon feed mechanism which is required for a two color printer of the ink ribbon type can be eliminated, and hence the production cost can be reduced. While a two color printer of the ink roll type has such advantages as described just above, it still has a following drawback.
In particular, in a two color printer in which two ink rolls are used, it is necessary to apply ink of a desired one of the ink rolls to a predetermined area of the type wheel. However, if the diameter of a type wheel is reduced as the printer size is reduced, the distance between character type elements for black and different character type elements for red both located along a periphery of the type wheel is reduced naturally, and hence a problem may occur that a mechanism for changing over the ink roll for a different color is complicated.